The present invention relates to a method of generating a test tone signal and a test-tone-signal generating circuit.
In audio reproduction, audio reproduction systems have been evolving from 2-channel stereo systems into 5.1-channel audio, 7.1-channel audio, and more-than-7.1-channel audio systems as digital audio technologies and audio visual (AV) devices have been developed. However, in such multi-channel audio systems, it becomes difficult for a user to appropriately and manually set the sound balance between channels, frequency characteristics, and others.
In this situation, sound field correction devices that automatically set the sound balance, the frequency characteristics, and others have been supposed. The sound field correction devices supply a test tone signal to the speakers of multiple channels, pick up reproduced sounds from the speakers with microphones, and correct the characteristics of the channels so that the sound balance, the frequency characteristics, and others of the reproduced sounds are appropriately set.
However, in order to perform the sound field correction, it is necessary to first check connection of the speakers. This is because the user fails to obtain information used for the sound field correction in a state in which the speakers are not connected to the apparatus even if the test tone signal is output.
In addition, for example, a reproduction apparatus capable of reproducing 7.1-channel audio signals is possibly used as a reproduction apparatus for 5.1-channel audio signals because of the arrangement of the speakers or the like. Accordingly, it is necessary to check the presence of non-connected speakers (channels that are not used) in multi-channel reproduction apparatuses.
Related arts are disclosed in, for example, Japanese Unexamined Patent Application Publication No. 2001-346299.
In the above setting or checking, a pink noise is generally used as the test tone signal. However, the pink noise is not ear-pleasing because the pink noise strikes the user's ear as noise burst. Furthermore, it is not acceptable that such a pink noise is output from a speaker each time a reproducing apparatus is used (is turned on).
It is desirable not to cause discomfort to a listener (user) in the checking of connection of speakers and to correctly check whether the speakers are connected.